I favor pre-finishing, but only because I find working overhead taxing. But keep in mind that there will be some touch-up work after installation. So not 100% pre-finished.
Also, pre-finishing eliminates most of the risk of seasonal wood movement exposing unfinished areas.
In any case, working with a helper will more than double your output.
I pre applied primer and first coated before my last install, then did finish coat after install. Any work that can be done on the ground is faster IMO
